Gym attire- Am I in the wrong?

I was told today by gym staff that I'm not allowed to wear jeans in the gym and that people have been complaining about what I wear. For context I'm from the US but am currently deployed to a European country, the gym is part of the hotel I've been staying at for the last several months. I'm definitely a beginner but i did go to the gym back home somewhat, but usually during my lunch wearing my uniform which is very common. Since being here I've been really locked in and hitting the gym 5 times a week. I usually just wear whatever I was already wearing since I don't own any "athletic" clothing. Usually its a button up shirt and either jeans, khakis, or linen pants. All of my clothing is natural fibers and fits well, doesn't limit ROM or my ability to lift whatsoever. In my opinion I don't feel the need to go out and buy a bunch of neon colored 200% polyester stuff just to lift weights and anybody who's got an issue should mind their own business. There's no posted dress code but buddy told me the way I dress is "not allowed".